Problem: Expand.
$\begin{aligned} ( x{-3})(x-4)&= x(x-4){-3}(x-4) \end{aligned}$ $\begin{aligned} \phantom{( x{-3})(x-4)}&=x^2-4x-3x+12 \\\\ &=x^2-7x+12 \end{aligned}$